Write it out:
-f: perldoc -f -X. If no file name is specified (as is the case here) checks if $_ contains the name of a plain file
>: Checks if the RHS is greater than the LHS
@+: In scalar context, returns the number of elements in @+
?: the conditional operator
*<: The glob for main::<
.: String concatenation operator
-&'_: Invokes a subroutine main::_. FYI, ' is the perl4 style package name separator. Try perl -MHTML'Template -e 1.
: : Continuing with conditional operator
$# : The output format for printed numbers
/ : Division operator
%! : %ERRNO; see perldoc perlvar
So, it is not impossible to understand if you put a little effort into it. Clearly, this is not how anyone should write programs, but there some benefit from people pushing the boundaries.
$# is no longer supported" on Perl 5.10 – Brad Gilbert Jul 31 '09 at 14:05